Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B64—AIRCRAFT; AVIATION; COSMONAUTICS
  • B64C—AEROPLANES; HELICOPTERS
  • B64C3/00—Wings
  • B64C3/26—Construction, shape, or attachment of separate skins, e.g. panels
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C21/00—Alloys based on aluminium
  • C22C21/12—Alloys based on aluminium with copper as the next major constituent
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D21/00—Casting non-ferrous metals or metallic compounds so far as their metallurgical properties are of importance for the casting procedure; Selection of compositions therefor
  • B22D21/002—Castings of light metals
  • B22D21/007—Castings of light metals with low melting point, e.g. Al 659 degrees C, Mg 650 degrees C
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
  • C21D1/26—Methods of annealing
  • C21D1/30—Stress-relieving
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/02—Making non-ferrous alloys by melting
  • C22C1/026—Alloys based on aluminium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C21/00—Alloys based on aluminium
  • C22C21/12—Alloys based on aluminium with copper as the next major constituent
  • C22C21/14—Alloys based on aluminium with copper as the next major constituent with silicon
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C21/00—Alloys based on aluminium
  • C22C21/12—Alloys based on aluminium with copper as the next major constituent
  • C22C21/16—Alloys based on aluminium with copper as the next major constituent with magnesium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
  • C22F1/057—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon of alloys with copper as the next major constituent

Definitions

• the invention relates to aluminum-copper-lithium alloy products, more particularly, such products, their manufacturing and use processes, intended in particular for aeronautical and aerospace construction.
• Aluminum alloy products are developed to produce high-strength parts for the aerospace industry and the aerospace industry in particular.
• Aluminum alloys containing lithium are very interesting in this respect, since lithium can reduce the density of aluminum by 3% and increase the modulus of elasticity by 6% for each weight percent of lithium added.
• their performance compared with the other properties of use must reach that of the alloys commonly used, in particular in terms of a compromise between the static mechanical strength properties (yield strength in tension and in compression, breaking strength) and the properties of damage tolerance (toughness, fatigue crack propagation resistance), these properties being in general antinomic.
• yield strength in tension and in compression, breaking strength the properties of damage tolerance (toughness, fatigue crack propagation resistance)
• the yield strength in compression is an essential property because it is decisive for the buckling characteristics.
• this characteristic is essential for the dimensioning and therefore the weight of the parts.
• No. 5,032,359 discloses a broad family of aluminum-copper-lithium alloys in which the addition of magnesium and silver, in particular between 0.3 and 0.5 percent by weight, makes it possible to increase the mechanical strength.
• US Pat. No. 7,438,772 describes alloys comprising, in percentage by weight, Cu: 3-5, Mg: 0.5-2, Li: 0.01-0.9 and discourages the use of higher lithium content because of degradation of the compromise between toughness and mechanical strength.
• US Pat. No. 7,229,509 describes an alloy comprising (% by weight): (2.5-5.5) Cu, (0.1-2.5) Li, (0.2-1.0) Mg, (0, 2-0.8) Ag, (0.2-0.8) Mn, 0.4 max Zr or other grain refining agents such as Cr, Ti, Hf, Se, V.
• US patent application 2009/142222 A1 discloses alloys comprising (in% by weight), 3.4 to 4.2% Cu, 0.9 to 1.4% Li, 0.3 to 0.7% of Ag, 0.1 to 0.6% Mg, 0.2 to 0.8% Zn, 0.1 to 0.6% Mn and 0.01 to 0.6% of at least one element. for the control of the granular structure. This application also describes a process for manufacturing spun products.
• the patent application WO2009 / 036953 relates to an aluminum alloy product for the structural elements having a chemical composition comprising, by weight%: Cu of 3.4 to 5.0, Li of 0.9 to 1.7, Mg from 0.2 to 0.8, Ag from about 0.1 to 0.8, Mn from 0.1 to 0.9, Zn to 1.5, and one or more elements selected from the group consisting of (Zr about 0.05 to 0.3, Cr 0.05 to 0.3, Ti about 0.03 to 0.3, Se about 0.05 to 0.4, Hf about 0.05 to 0.4 ), Fe ⁇ 0.15, Si ⁇ 0.5, normal and unavoidable impurities.
• the patent application WO 2012/085359 A2 relates to a process for producing aluminum-based alloy rolled products comprising 4.2 to 4.6% by weight of Cu, 0.8 to 1.30%. by weight of Li, 0.3 to 0.8% by weight of Mg, 0.05 to 0.18% by weight of Zr, 0.05 to 0.4% by weight of Ag, 0.0 to 0% , 5% by weight of Mn, at most 0.20% by weight of Fe + Si, less than 0.20% by weight of Zn, at least one element selected from Cr, Se, Hf and Ti, the amount of said element , if selected, being from 0.05 to 0.3% by weight for Cr and for Se, 0.05 to 0.5% by weight for Hf and from 0.01 to 0.15% by weight for Ti, the other elements at most 0.05% by weight each and 0, 15% by weight in total, the rest aluminum, comprising the steps of production, casting, homogenization, rolling with a temperature above 400 ° C, setting in solution, quenching, traction between 2 and 3.5% and income.
• the patent application US2012 / 0225271 A1 concerns wrought products with a thickness of at least 12.7 mm containing 3.00 to 3.80 3.00 to 3.80 by weight.% Cu, from 0.05 to 0. , Wt% Mg, from 0.975 to 1.385 wt% Li, wherein -0.3 * Mg-0.15Cu +1.65 ⁇ Li ⁇ -0.3 * Mg-0.15Cu + 1.85, from 0.05 to 0.50 by weight.
• the grain structure control element is selected from the group consisting of Zr, Se, Cr, V, Hf, other land elements Rare, and combinations thereof, up to 1.0% by weight% Zn, up to 1.0% by weight% Mn, up to 0.12% by weight% Si, up to 0%. 15 wt.% Fe, up to 0.15 wt.% Ti, up to 0.10 wt. % of other elements with a total not exceeding 0.35% by weight.
• a first object of the invention is a process for manufacturing a spun, rolled and / or forged product based on aluminum alloy in which:
• an income of said product is obtained by heating at a temperature of 140 to 170 ° C for 5 to 70 hours.
• Another object of the invention is a product spun, rolled and / or forged aluminum alloy obtainable by the method according to the invention having a thickness of at least 12 mm, a yield strength in compression in the longitudinal direction of at least 645 MPa and elongation in the longitudinal direction of at least 7%.
• Yet another object of the invention is an extrados structure element incorporating at least one product according to the invention or made from such a product.
• Figure 1 Compromise of properties between the yield strength in compression and the toughness for the sheets of Example 1.
• Figure 2 Schematic of test specimens used for hole fatigue tests. Dimensions are given in mm.
• Figure 3 Wohler curves obtained with the alloys 2, 4 and 5 in the direction L-T.
• the static mechanical characteristics in tension in other words the tensile strength R m , the conventional yield strength at 0.2% elongation R p0; 2 , and the elongation at break A%, are determined by a tensile test according to standard NF EN ISO 6892-1, the sampling and the direction of the test being defined by the standard EN 485-1.
• the yield strength in compression was measured at 0.2% compression according to the standard
• the stress intensity factor (KQ) is determined according to ASTM E 399.
• ASTM E 399 gives the criteria for determining whether KQ is a valid value of K 1 ( >)
• KQ values obtained for different materials are comparable with each other as long as the elasticity limits of the materials are of the same order of magnitude.
• the Walker equation was used to determine a representative maximum stress value of 50% non-break at 100,000 cycles. To do this a fatigue quality index (IQF) is calculated for each point of the Wôhler curve with the formula
• N the number of cycles to failure
• N 0 the number of cycles to failure
• n -4.5.
• the IQF corresponding to the median is reported, ie 50% rupture per 100,000 cycles.
• the static mechanical tensile characteristics, the compression elasticity limit and the stress intensity factor are measured at half thickness of the products.
• EN 12258 Unless otherwise specified, the definitions of EN 12258 apply.
• the present invention it is possible to improve the yield strength in compression of copper magnesium aluminum alloys whose copper content is between 4.2 and 5.2% by weight and the lithium content between 0 , 9 and 1.2% by weight by decreasing the magnesium content, relative to the contents of at least 0.3% by weight known and in simultaneously increasing the dissolution temperature.
• the decrease in the magnesium content the expected consequence of which is a decrease in the static mechanical properties, makes it possible for the alloys of the invention, on the contrary, to increase the static mechanical properties.
• the alloy according to the invention contains 4.2 to 5.2% by weight of Cu.
• a minimum copper content of 4.3% and preferably 4.4% by weight is advantageous so as to obtain high static mechanical properties.
• a maximum copper content of 5.0% and preferably 4.8% by weight is advantageous so as to obtain sufficient elongation and toughness.
• the alloy according to the invention contains 0.9 to 1.2% by weight of Li.
• a minimum lithium content of 1.0% and preferably 1.03% by weight is advantageous so as to obtain mechanical properties. high static.
• a maximum lithium content of 1.15% and preferably 1.10% by weight is advantageous so as to obtain sufficient elongation and toughness.
• the alloy according to the invention contains 0.1 to 0.25% by weight of Mg.
• a minimum magnesium content of 0.15% and preferably 0.20% by weight is advantageous so as to obtain high static mechanical properties.
• a maximum magnesium content of 0.24% by weight is advantageous so as to further increase the solution temperature. According to the present inventors, it is possible that the magnesium content according to the invention results in an increase in the solidus temperature and thus makes it possible to increase the dissolution temperature and thus improve the dissolution of the copper and the solution. fraction of hardening phases after income.
• Very high tensile and compressive yield strengths sometimes greater than 700 MPa in the case of extruded products, obtained with the alloys according to the invention while maintaining a formability, the remaining elongation of at least 7%, are probably related notably to the excellent dissolution of copper.
• the alloy according to the invention contains 0.1 to 0.3% by weight of Ag.
• a minimum silver content of 0.15% and preferably 0.20% by weight is advantageous.
• a maximum silver content of 0.25% by weight is advantageous. The present inventors believe that contrary to what is expected, the relatively low silver content allows to further increase the static mechanical resistance by helping to increase the dissolution temperature.
• the alloy according to the invention contains 0.08 to 0.18% by weight of Zr. Preferably, the alloy according to the invention contains 0.11 to 0.18% by weight of Zr. A minimum zirconium content of 0.13% by weight is advantageous. A maximum zirconium content of 0.17% by weight is advantageous. The alloy according to the invention contains 0.01 to 0.15% by weight of Ti. A minimum titanium content of 0.02% by weight is advantageous. A maximum titanium content of 0.1% by weight and preferably 0.05% by weight is advantageous.
• zirconium and titanium contributes to a substantially unrequistallized structure which is advantageous.
• the addition of titanium also contributes to controlling the granular structure during casting.
• the alloy according to the invention may contain up to 0.2% by weight of zinc.
• the zinc content is less than 0.05% by weight.
• the alloy according to the invention can contain up to 0.6% by weight of manganese.
• the manganese content is between 0.2 and 0.5% by weight and preferably between 0.3 and even 0.35 and 0.45% by weight.
• the addition of manganese makes it possible, in the case of the manufacture of sheets, to simultaneously improve the yield strength in compression and the toughness, especially in the L-T direction, which is advantageous.
• the addition of manganese also makes it possible, in the case of extrusion profile production, to improve, in particular, toughness in the T-L direction.
• the content of Fe and Si of the alloy according to the invention is less than or equal to 0.1% by weight each, advantageously the iron content is less than 0.06% by weight and the silicon content is less than 0.04% by weight.
• the other elements have a content less than or equal to 0.05% by weight each and 0.15% by weight in total, the rest is aluminum.
• a liquid metal bath of composition according to the invention is produced and then a raw form, such as a rolling plate, a spinning billet or a forge blank, is cast from said metal bath liquid.
• the method according to the invention may comprise steps known to those skilled in the art such as scalping or heat treatments for relaxing cast plates.
• the raw form is homogenized by a heat treatment in which the mid-thickness temperature of the raw form reaches at least 510 ° C for a period of at least 10 hours.
• the alloy according to the invention in particular because of the low content of magnesium and silver, makes it possible to homogenise at a high temperature without causing partial local melting, also called burn.
• the temperature at mid-thickness of the raw form reaches at least 515 ° C. for a period of at least 10 hours.
• the homogenization is carried out with at least two stages, typically at least a first stage at a temperature of between 495 ° C. and 505 ° C.
• said raw form is deformed hot and optionally cold in a spun, rolled and / or forged product.
• the heat distortion temperature is typically at least 350 ° C and preferably at least 400 ° C.
• Said product is then dissolved at a temperature of at least 515 ° C, preferably at least 520 ° C and in some cases at least 522 ° C.
• the dissolution time is adapted to the thickness of the product so that the dissolution temperature is reached mid-thickness of the product, preferably for a period of at least one hour. It is technically possible to dissolve at such a high temperature with alloys having a composition similar to that of the alloys according to the invention with respect to Cu, Li, Zr, Ti, Zn and Mn but higher in Mg. and Ag but this results in a degradation of the mechanical properties due to the inevitable burns, in particular the elongation and the tenacity are decreased.
• the maximum temperature value that can be used for the dissolution treatment can be evaluated by differential calorimetry (DSC) on the product resulting from the hot deformation step.
• DSC differential calorimetry
• the advantage of the alloys according to the invention is to reach a maximum temperature value that can be used for the high-solubility treatment without the risk of burns, the temperature rise rate being adapted to the geometry of the product by the human being. profession according to his general knowledge.
• the solution temperature is less than 530 ° C., when the treatment is carried out in a single stage.
• the present inventors have however observed that with the alloys according to the invention, it is possible to carry out a dissolution with a first stage at a temperature of between 515 ° C. and 520 ° C. and a second plateau at a temperature of at least 530 ° C and preferably at least 535 ° C and obtain in particular an improved compromise between elongation and elastic limit.
• the product After dissolution, the product is quenched, typically by spraying or immersion with water at room temperature.
• the product thus dissolved and quenched undergoes stress relieving with a permanent deformation of 0.5 to 5%.
• the controlled tensile stress relieving is carried out with a permanent deformation of less than 2% and advantageously of 0.5 to 1.5%.
• This embodiment with moderate permanent deformation may, however, have the disadvantage of requiring a long income period and impairing the productivity of the process.
• controlled tensile stress relieving is carried out with a permanent deformation of between 2% and 4%.
• the product thus trapped finally receives an income by heating at a temperature of 140 to 170 ° C for 5 to 70 hours.
• the income can be made in one or more levels.
• the controlled tensile stress relieving is performed with a permanent deformation less than 2% the income is made between 150 and 160 ° C for a period of 40 to 60 hours.
• the controlled tensile stress relieving is carried out with a permanent deformation greater than 2% the income is made between 150 and 160 ° C for a period of 10 to 40 hours.
• the products thus obtained preferably have a substantially non-recrystallized granular structure.
• substantially uncrystallized granular structure refers to a granular structure such that the degree of recrystallization between 1 ⁇ 4 and 1 ⁇ 2 thickness is less than 30% and preferably less than 20%.
• the products according to the invention preferably have a thickness of at least 12 mm.
• the thickness of the spun products is defined according to EN 2066: 2001: the section transversal is divided into elementary rectangles of dimensions A and B; A being always the largest dimension of the elementary rectangle and B can be considered as the thickness of the elementary rectangle.
• the sole is the elementary rectangle having the largest dimension A.
• the thickness of the products according to the invention is at least 15 mm and less than 50 mm.
• the process according to the invention combining, in particular, the composition according to the invention and the heat treatment of homogenization and dissolution in solution according to the invention makes it possible to obtain a spun, rolled and / or forged product made of aluminum alloy having a thickness of at least 12 mm, a compressive elasticity limit in the longitudinal direction of at least 645 MPa and preferably at least 650 MPa and an elongation in the longitudinal direction of at least 7% and preferably at least 8%.
• the spun products according to the invention advantageously have an L-direction compressive yield stress of at least 680 MPa, an L-direction tensile yield strength of at least 680 MPa and a KQ toughness (T L), of at least 17 MPa.
• the rolled products according to the invention, the thickness of which is at least 20 mm advantageously have a compressive strength limit in the L direction of at least 650.
• the rolled products according to the invention advantageously have a limit of elasticity. in compression in the direction L of at least 653 MPa and preferably at least 655 MPa and a tenacity Q (LT) of at least 20
• the extrados structural elements incorporating at least one product according to the invention or manufactured from such a product are advantageous.
• a "structural element” or “structural element” of a mechanical construction is called a mechanical part for which the static and / or dynamic mechanical properties are particularly important for the performance of the structure, and for which a structural calculation is usually prescribed or realized.
• These are typically elements whose failure is likely to endanger the safety of said construction, its users, its users or others.
• the extrados structural elements include the upper wing skin and the upper wing stringers (stiffeners).
• Example 1 In this example, five plates 406 x 1520 mm in size, the composition of which is given in Table 1, were cast. Alloys 1, 2 and 3 have a composition according to the invention. Alloys 4 and 5 have a reference composition.
• the plates were homogenized. Following preliminary tests by differential calorimetry, different conditions were used for the different plates so as to achieve maximum homogenization without burning.
• the alloy plates 1, 2 and 3 were homogenized for 15 h at 500 ° C and then 16 h at 516 ° C. Plates 4 and 5 were homogenized for 15 h at 492 ° C.
• the plates were hot rolled at a temperature above 420 ° C to obtain 25 mm thick sheets. After hot rolling, differential calorimetry tests were again performed to determine the solution temperature. It has been shown that the sheets according to the invention can withstand a solution dissolution temperature of at least 515 ° C. whereas for the reference sheets a risk of burn is present at this temperature and a solution dissolution temperature of less than 515 ° C was needed.
• the sheets were dissolved at 516 ° C (alloys 1 to 3), 512 ° C (alloys 4) and 509 ° C (alloy 5) for about 5 hours and then quenched with water at 20 ° C.
• the alloy sheets 1 and 2 were then trimmed by about 3%.
• the alloy sheets 4 and 5 were trimmed by 4%.
• the static mechanical properties measured at mid-thickness obtained after various conditions of income at 155 ° C are given in Table 2 and shown in Figure 1.
• billets with a diameter of 139 mm were taken from alloy plates 1 and 2.
• the billets were homogenized at 515 ° C., spun in the form of 54.6 ⁇ 16 mm bars at 460 ° C. then solutioned for 4 hours at 520 ° C and quenched with water.
• the bars thus obtained were drawn with a permanent elongation of 3%, then they were returned to 15h or 25h at 155 ° C.
• the mechanical characteristics measured in the L-direction at mid-thickness are presented in Table 4.
• the controlled tensile conditions were varied for an alloy sheet 2 25 mm thick dissolved for 5 h at 516 ° C and then quenched with water at 20 ° C.
• the sheets underwent a controlled pull with a permanent elongation of 1%, 2.1%, 3.5% or 4.5%. Different durations of income at 155 ° C were carried out to find the optimal compromise between yield strength in compression and toughness for each rate of permanent elongation. The results obtained are shown in Table 5.
• Example 2 the fatigue properties on test pieces with holes for alloys 2, 4 and 5 of Example 1 were evaluated. 25 mm thick sheets were laminated, dissolved and triturated as described in FIG. Example 1. The alloy sheet 2 was tempered for 25 hours at 155 ° C, the alloy sheets 4 and 5 experienced a 22 hour income at 155 ° C.
• the product according to the invention in alloy 2 has a significantly improved IQF compared to reference products in alloys 4 and 5

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